the common things on the 8 are water pump and ps pump. ps pump gets a fair bit of heat when extractors are installed, so some sheilding is recommended. 8's with a few kms can have ticking lifters on startup...like the 6's. 90% of the time, this can be fixed with engine flush and thin oil.

the 8's have a pritty much bullet proof bottom end, provided they have been treated right.

as for performance, we lined up a 5 speed ED 6cyl with 3.27 free wheeler, (lowered was the only mod) with 160k and a v8 falc with (3.23 lsd) stock everything 220k (country kms) and they were pritty much line ball.

There is a reason why the XR8s are worth more. Personally I'm not aware there is a huge difference in price (certainly not enough to make it a deciding factor). It comes down to personal preference really. I like a V8, not everyone does.

When I was looking to buy I saw an EL XR6 for $15,000 and an EL XR8 for $14,900 ono. Both were private sales, and both were in very good condition.

My point is that the price is also relative to the seller's [sometimes] dillusion of their car's value.

If you want the XR8, just look around for a week or two, though I would offer the same advice for the XR6.

go the V8. you can't beat the rumble of a V8. However they do cost more to run higher fuel cost; dearer rego & insurance & some parts can be more expensive; all things worth considering if your mates on a budget